Track indication system



lzvmvrozz H0515. Harlow By M N m $1 kw Q E N TWNMM: mu MN m A Q m r 11K $5M @EU kw M mm afi m, w R N Q March 28, 1944.

His'Arromm Patented Mar. 28, 1944 UNITED STATES PATENT OFFICE TRACK INDICATION SYSTEM Application June 25, 1942, Serial No. 448,331

1 Claim.

My invention relates to track indication systems, and more particularly to apparatus for continuously indicating the trafiic condition of a stretch of railway track.

A stretch of railway track is frequently pro vided with automatic wayside signals for governing the movements of trains in a normal direction. Train movements in the reverse direction over such a stretch of track are permitted by train orders or the equivalent, it being required that the operator take such steps as necessary to inform himself that such stretch is not occupied by a train moving in the normal direction before he permits a train to move into the stretch in the reverse direction. Frequently the stretch of track through which the train must move against traffic is of considerable length and indication means heretofore used for such a length of track requires repeaters due to the voltage drop of the long line circuit.

Accordingly, an object of my invention is the provision of novel and improved continuous track indication means.

Another object of my invention is the provision of novel and improved means for indicating the trafilc condition of a relatively long stretch of railway track without requiring repeater equipment.

Again, an object of my invention is the provision of novel apparatus wherewith different indications are provided for different portions of a stretch of railway track and a false indication due to a circuit cross or ground is avoided.

Other objects, features, and advantages of apparatus emboding my invention will appear as the specification progresses.

To accomplish the foregoing objects I provide a stretch of railway over which trafiic normally moves in a given direction and which is formed with track sections each having a track relay, with a manually controlled signal located at the exit end of the stretch to govern traffic into the stretch in the reverse direction and two line circuits each extending throughout the stretch. One of these line circuits is preferably controlled through a front contact of each track relay of a group of the sections near the exit end of the stretch and the other line circuit is controlled through a front contact of each of the track relays of the entire stretch. A direct current source and a coder are placed at the entrance end of the stretch and are connected to the line circuits to supply one line circuit with current of one polarity coded at a first code rate and to supply the other line circuit with current of the other polarity coded at a second code rate. At the exit end two polar code following relays are connected one to each line circuit. These code following relays are preferably of the biased polar type of high sensitivity to be operated directly by current supplied to the circuit at the entrance end of the stretch although it may be of considerable length. Each relay is poled to be operated only by current of the polarity supplied to the respective line circuit. Each code following relay governs a decoding relay through a circuit tuned to energize the relay only by energy of the corresponding code rate. The decoding relays are used in turn to govern two indicators one of which indicates occupancy of the stretch and the other occupancy of the preselected portion near the exit end of the stretch. Such indicators serve to provide the operator with information as to traffic conditions so that he may properly govern the signal.

I shall describe one form of apparatus embodying my invention and shall then point out the novel features thereof in claim.

The accompanying drawing is a diagrammatic view showing one form of apparatus embodying my invention.

Referring to the drawing, the reference characters la and lb designate the track rails of a stretch of railway track extending between two locations D and Z, and over which stretch of track trafiic normally moves in the direction indicated by an arrow. The track rails la and lb are formed by the usual insulated rail joints into consecutive track sections, of which sections only the two sections DE and E-F next adjacent the location D, that is, the entrance end of the stretch, and the two track sections XY and Y-Z next adjacent the location Z, that is, the exit end of the stretch, are shown in the drawing, since these are sufilcient for a full understanding of my invention. The intervening sections of the stretch are indicated :by dotted lines for the rails la and lb. Each track section is provided with a track circuit including a source of current, such as a battery 3, connected across the rails at one end of the section, and a track relay designated TR plus a prefix corresponding to the location, connected across the rails at the other end of the section. It is to be understood, of course, that my invention is not limited to a stretch of track of any particular length, or of any particular number of track-circuited sections.

These track circuits may be a part of an automatic wayside signal system of which the wayside signals are designated S plus a sufiix corresponding to the location, which wayside signals are controlled by control apparatus for governing trains moving in the normal direction of trafiic. The control apparatus for the wayside signals S is not shown since it forms no part of my invention and it may be that provided by any one of several well-known automatic wayside signal systems. A manually controlled signal BSZ is provided at location Z for governing trains moving into the stretch of track against the normal direction of traffic. Signal BSZ may be of any suitable type capable ofdisplaying a stop and a proceed indication," and may begoverned in any convenient manner. As disclosed, signal BSZ is a three-position color light signal capable of dis H return wire CL is connected to the mid terminal C of battery Bl line wire Ll is connected to the positive terminal of battery Bl. through the contact lZt-IZUa of coder CT, and line wire L2 is connected to the negative terminal of battery Bl through the contact l8B-l8lia of coder CT. It

follows that direct current of one polarity, which I shall call normal polarity, is supplied to the circuit including line wires LI and CL, the coding jofthe current being'of the 120 code rate; and direct current'of the opposite polarity, which I shall call reverse polarity, is supplied to the cirreadily understood by an inspection. of the draw ing. Thus, an operator at location Z can control the signal BSZ to permit a train to enter the stretch of track between locations D and Z against the normal direction of traflic. It is to be understood, of course, that the operator at location Z would take whatever steps necessaryto assure himself th'atthe stretch is unoccupied by any train moving in the normal direction of trafiic, before he controls signal BSZ to permit a train movement reverse to the normal direction of traffic. Furthermore, written train orders may be required in addition to the display of signal BSZ to permit a reverse train movement.

To inform the operator at location Z of the traffic conditions of the stretch of track between locations D and Z, I provide according to my invention indication means that continuously indicates the traffic conditions of the stretch. This indication means comprises a three-wire line circuit, a source of coded current, decoding means and indicators. The three-wire line circuit includes a first and a second control line wire LI and L2, respectively, and a common return wire CL. These line wires Ll, L2 and CL extend throughout the stretch and are formed into two circuits, one of which includes the control wire LI and common wire CL, and the other of which includes control wire L2. and common wire CL. For reasons to appear hereinafter, front contacts 1 and 8 of track relays XTR and YTR, respectively, are interposed in line wire LI, and front contacts 9, H), II and I2, of track relays DTR, ETR, XTR and YTR, respectively, are interposed in line wire L2. It will be understood that contacts of the track relays for the intervening sections would be interposed in either of both line wires LI and L2 as predetermined.

The source of coded current comprises a battery BI and a coder or code transmitter CT which are preferably located at the entrance end D of the stretch. Battery BI is preferably of the socalled split battery type, whose mid terminal is indicated at C0, while its positive and negative terminals are identified by plus and minus signs. Battery Bl would be of any suitable voltage. Coder CT may be of any one of several wellknown constructions; and it is disclosed as of the relay type provided with two contact members I and I80 which are cyclically operated at different preselected code rates as long as the operating winding is energized by a suitable source of current, such as a battery, whose terminals are indicated at B and C. I shall assume by way of illustration that contact member I29 is operated to periodically engage a fixed contact I2lla at the code rate of 120 times per minute, and contact member I80 is periodically operated to engage a fixed contact IBM at the code rate of 180 times per minute. It is to be understood that my invention is not limited to these particular code rates, and other code rates and manner of coding the current can be used if desired. The common cuit including line wires L2 and CL, the coding being of the 180 code rate.

The decoding means is preferably located at the exit end 2 of the stretch andcomprises two code following relays CF! and CM, two decoding transformers TI and T2, and two decoding re,- lays LR and AR. Code following relays CPI and CF2 are preferably biased polar relays, and as here disclosed, the armature of each of these relays is spring biased to a. normal right-hand position, and is operated to a reverse or left-hand position only when energy of positive polarity is supplied to the left-hand terminal of the winding of the relay. Current of positive polarity when applied to the right-hand terminal of the relay winding aids the bias in retaining the armature of the relay at the normal right-hand position. Code following relay CFI is connected across line wires LI and CL, and code following relay CFZ is connected across line wires L2 and CL. The

connection of relay CFI is such that it is operated in response to the coded direct current of normal polarity supplied to theline wires LI and CL, and

' the connection of code following relay CFZ is such that it is operated in response to the coded direct current of reverse polarity supplied to the line wires L2 and CL in the manner explained hereinbefore. Such biased polar relays are char:

acterized by high sensitivity and reliable operation over a wide variation in the voltage of the current supplied thereto. Thus relays CFI, and CF2 can be used in a line circuitof a relatively great length. That is, the stretch of track D- Z along which the line circuit extendsmay be many miles in length and the code following relays CFI and CFZ can be operated by a line circuit extending the full length of the stretch andre- .peater equipment is not required. In other words, the stretch D-Z may be of such length that it would not be possible to control the usual form of code following relay by a line circuit extending the entire length of the stretch on account of the voltage drop in the line circuit, and

it would-be necessary to provide'repeater relays at one or more locations.

Code following relay CFI controls at its normaland reverse polar contacts l3 and M the supply of direct current to the two portions-of primary winding l 5 of decoding transformer Tl, with the result that an alternating electromotive force is induced in secondary I6 of transformer TI, the

frequency of which electromotive force corresponds to the code rate at which relay CFl. is

operated. That is, in the case here assumed for illustration, the frequency of the electromotivea full wave rectifier l9. Condenser I! and in ductance I8 are tuned to resonance at the frequency corresponding to the 120 code rate of operation of relay CFI and consequently the decoding relay LR is energized and. picked up only in response to current supplied to code following relay CFI through the circuit including line wires LI and CL. Similarly, code following relay CF2 controls at its polar contacts and 2| the supply of direct current to the two portions of primary winding 22 of decoding transformer T2, and an electromotive force is induced in secondary winding 23 of transformer T2, the frequency of which electromotive force corresponds to the 180 code rate at which code following relay CF2 is operated. Winding 23 of transformer T2 is connected to a tuned circuit comprising a condenser 24 and an inductance 25, at least a portion of inductance 25 being connected to decoding relay AR through a full wave rectifier 26. Condenser 24 and inductance 25 are tuned to resonance at the frequency corresponding to the 180 code rate of operation of relay CF2, with the result that relay AR is energized and picked up only in response to the current supplied to relay CFZ through the circuit including line wires L2 and CL.

An indicator NI is controlled by an obvious circuit including front contact 21 of relay LR, and another indicator N2 is controlled by an obvious circuit including front contact 28 of relay AR in series with front contact 29 of relay LR.

When the entire stretch DZ is unoccupied and all the track relays are picked up, both line circuits are complete so that both code following relays CFI and CFZ are operated at the respective code rates, with the result that both relays LR and AR are energized and both indicator lamps NI and N2 are illuminated to indicate the unoccupied trafiic condition of the stretch. With such information at hand, it would be safe for the operator at location Z to control signal BSZ to permit a train movement in the reverse di rection through the stretch. In the event the portion of the stretch near the exit end Z is occupied and either one or both of the track relays XTR and YTR are released, both line cricuits are open and both code following relays CFI and CF2 are inactive, with the result that both relays LR and AR are deenergized and both indicator lamps NI and N2 are dark. With such information at hand, the operator at location Z would know that it is unsafe to permit a reverse train movement. In the event the portion of the stretch near the entrance end D is occupied, so that either one or both of the track relays DTR and ETR are released, but the portion of the stretch near the exit end Z is unoccupied so that the track relays X'I'R and YTR are picked up, the circuit including line wires LI and CL is complete and the circuit including line wires L2 and CL is open. Code following relay CFI is operated, but code following relay CF2 is inactive, with the result that indicator lamp NI is illuminated, but indicator lamp N2 is dark. If this display of the indicators NI and N2 is caused by a train moving in the normal direction of traffic, it would be unsafe for the operator to permit a reverse train movement. However, if this condition of the indicator lamps is caused :by a first train moving through the stretch in the reverse direction, such indication of the indicators would be useful to the operator in the event a second or following train is to be permitted to move through the stretch in the reverse direction, the

illumination of indicator lamp NI informing the operator that the first train has advanced to a predetermined portion of the stretch and it is safe for him to permit a second reverse train movement.

In connection with the line circuit here provided, it is to be pointed out that a cross between line wires LI and L2 would create no false operation of either relay CFI and CF2 because of the polarity of the coded current supplied to the two different circuits. Also, grounds on the line wires such as might cause false operation of either code following relay would create no false indication by lamp NI or N2 because of the tuned circuits through which the decoding relays LR and AR are energized.

Apparatus here disclosed has the advantages that two distinct continuous indications of traffic conditions of a stretch of track are provided by a three-wire line circuit, reliable operation is obtained over a line circuit of considerable length without repeater equipment, and false indications due to crosses or grounds on the line wires are avoided.

Although I have herein shown and described but one form of apparatus for track indication systems embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claim without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

In combination, a stretch of railway track over which traffic normally moves in a given direction formed with consecutive track circuited sections each provided with a track relay, a signal located at the exit end of the stretch for at times directing a train into the stretch in the reverse direction, a first line circuit extending through said stretch and having interposed therein front contacts of the track relays of a first preselected group of the sections near the exit end of the stretch, a second line circuit extending through said stretch and having interposed therein front contacts of the track relays of all of the sections of the stretch, supply means at the entrance end of the stretch connected to said line circuits to supply to the first line circuit direct current of normal polarity coded at a first code rate and to supply to the second line circuit direct current of reverse polarity coded at a second code rate, a first polar code following relay at the exit end of the stretch connected to said first line circuit and operated only by current of normal polarity, a second polar code following relay at the exit end of the stretch connected to said second line circuit and operated only by current of reverse polarity, said polar relays characterized by high sensitivity to operate through said line circuit directly by current supplied by said supply means, a first decoding relay controlled by said first code following relay and energized only by energy of said first code rate, a second decoding relay controlled by said second code following relay and energized only by energy of said second code rate, and a first and a second indicator governed by said first and second decoding relays respectively to indicate by said second indicator occupancy of the stretch and by said first indicator the presence of a train near the exit end of the stretch to a d t e ope a r n governing said signal.

ROY E. HARLOW. 

